POLLUTION AND ECOLOGICAL RISK ASSESSMENT OF HEAVY METAL IN SOIL AROUND COAL MINE IN SUZHOU CITY

By means of field sampling and laboratory analysis, the concentrations of Zn, Cr, Cd, Pb, Cu, As and Hg of soil around coal mine in Suzhou City were determined. Assessment of heavy metal pollution was analysized using potential ecological risk index. The results show : 1) All kinds of heavy metals contents decrease with the distance increasing, and the regional differentiation of heavy metals contents was obvious, among them, Pb ranging 6.42 similar to 18.90 mg/kg, Cd ranging 0.19 similar to 0.56 mg/kg, and Hg ranging 0.83 similar to 2.93 mg/kg, the variation coefficient of them reached 37.47%, 31.95% and 26.71%, respectively. 2) The contents of heavy metals demonstrated the following order: Cr>Zn>Cu>As>Pb>Hg>Cd. Except Zn and Cu, other elements contents are higher than the National Environmental Quality Standard 2, Cr 2.94 similar to 7.70 times, Hg 1.66 similar to 5.86 times, Cd 0.95 similar to 2.90 times. Comparison with regional soil environmental background values, Zn 1.22 times, Cr 2.51 times, Cd 1.79 times, Pb 1.36 times, Cu 1.50 times, As 1.17 times and Hg 3.80 times. 3) Potential ecological risk level of soil in four coal mines belong to moderate, the order as follows: Tanyuan > Qi'nan > Luling > Zhuxianzhuang. Cd and Hg were the most seriously ecological hazard factors. The level of heavy metal pollution in soil is declining with the distance increasing and coal mining is an important source of heavy metals in soil.